Peroxide crosslinked butyl rubber composites using TEMPO and sorbates

Peroxide curing can provide rubber products with good thermal aging resistance, low compression set and light color. But butyl rubber (IIR) and bromobutyl rubber (BIIR) will incur severe main chain degradation when using a peroxide as a curing agent. The presence of 2,2,6,6-tetramethylpiperidinyl-N-oxyl (TEMPO) and in situ formed zinc disorbate (ZDS) in dicumyl peroxide cured BIIR system can inhibit the degradation of BIIR without compromising the curing extent of BIIR vulcanizates. ZDS is grafted on BIIR, while TEMPO functions as a free radical scavenger and nitroxide mediator for the grafting reaction. The in situ formation and grafting reaction of ZDS in BIIR are characterized by FTIR, XRD and NMR spectroscopy. In the presence of TEMPO and ZDS, BIIR does not suffer degradation but exhibits a continuous increase in torque and crosslink density with time during the post-cure period. The presence of TEMPO could effectively improve the thermal stability and aging resistance of BIIR vulcanizates. The study provides an effective route to avoid the degradation and promote the crosslinking of BIIR that can easily incur β-scission when reacting with peroxides.